Separate README file for each component, fixes #11

Author: igorw

README.md

@@ -0,0 +1,58 @@
+# EventLoop Component
+
+Event loop abstraction layer that libraries can use for evented I/O.
+
+In order for async based libraries to be interoperable, they need to use the
+same event loop. This component provides a common `LoopInterface` that any
+library can target. This allows them to be used in the same loop, with one
+single `run` call that is controlled by the user.
+
+In addition to the interface there are some implementations provided:
+
+* `stream_select`: This is the only implementation which works out of the box
+  with PHP. It does a simple `select` system call. It's not the most performant
+  of loops, but still does the job quite well.
+
+* `libevent`: This uses the `libevent` pecl extension. `libevent` itself
+  supports a number of system-specific backends (epoll, kqueue).
+
+All of the loops support these features:
+
+* File descriptor polling
+* One-off timers
+* Periodic timers
+
+## Usage
+
+Here is an async HTTP server built with just the event loop.
+
+    $loop = React\EventLoop\Factory::create();
+
+    $server = stream_socket_server('tcp://127.0.0.1:8080');
+    stream_set_blocking($server, 0);
+    $loop->addReadStream($server, function ($server) use ($loop) {
+        $conn = stream_socket_accept($server);
+        $data = "HTTP/1.1 200 OK\r\nContent-Length: 3\r\n\r\nHi\n";
+        $loop->addWriteStream($conn, function ($conn) use (&$data, $loop) {
+            $written = fwrite($conn, $data);
+            if ($written === strlen($data)) {
+                fclose($conn);
+                $loop->removeStream($conn);
+            } else {
+                $data = substr($data, 0, $swritten);
+            }
+        });
+    });
+
+    $loop->addPeriodicTimer(5, function () {
+        $memory = memory_get_usage() / (1024*1024);
+        $formatted = number_format($memory, 3).'K';
+        echo "Current memory usage: {$formatted}\n";
+    });
+
+    $loop->run();
+
+**Note:** The factory is just for convenience. It tries to pick the best
+available implementation. Libraries `SHOULD` allow the user to inject an
+instance of the loop. They `MAY` use the factory when the user did not supply
+a loop.